Re: crown vic needs a little more oomph
As Stroker McGurk said, "speed costs, how fast do you want to go?"
I too have a charcoal grey '05 sport, one of a few with factory sunroof.
Not a lot can be done with the 4.6, and if you go too steep on the rear gears, your PCM, speed control, not to mention gas mileage, will be a problem.
Torque is what moves these two ton cars and a 5.4 is the way to go. I have built and installed two 5.4's in CV's, and they will fry the tires with stock 3.23 gears. A stock 5.4 is a dog, but you can gain an extra 100 HP and even more torque with Trick Flow heads (use the small CC heads for higher comp ratio) and cams. Degree the cams, I found them to be off a couple of degrees out of the box, use the stock intake with adaptor plates and a 70MM throttle body. Keep the stock exhaust, but remove the resonators. Make sure your trans is in good shape and don't forget to turn off the traction control. All else is bolt up, except the exhaust "H" pipe will have to be widened about 1/2-3/4 (wait until you get it in and measure).
Your C/V will never be fast, but you will gain the respect of every BM(W?) and MB driver in the neighborhood! The down side, plan on 5 G's if you do it all yourself.